1. Field of the Invention
The present invention relates to an image-processing method, an image-processing apparatus, and an image-processing program product.
2. Description of the Related Art
With the recent improvement of performance of ink jet printers and digital cameras, it has become possible for us to print images in the same quality as silver-film photographs. The subjects of printing here are digital images, which can easily be retouched; accordingly, we usually retouch images for higher quality by using photo retouch software, printer drivers, etc. As such retouch requires proficiency of a certain degree, various kinds of automatic retouching have been realized. For example, the quantities of characteristics are extracted from an image, the tendencies of gradation of the image are grasped by analyzing the quantities of characteristics, and the data of the image are revised to change the tendencies of gradation (See, for example, Japanese Unexamined Patent Publication No. 2000-36043).
The above prior art has the following problem. If an artificial image is added to a natural image, the prior art grasps the tendencies of gradation of the natural image wrongly and processes the natural image inappropriately.
An artificial image of a letter, line, pattern, or the like is often composed by collecting a plurality of pixels of a single color. Accordingly, if the prior art grasps the tendencies of gradation (for example, the histogram of brightness) of a natural image containing such an artificial image, tendencies of gradation different from those of the natural image are grasped because of the high frequency of appearance of a certain value of brightness and so on. Accordingly, the prior art makes inappropriate processing or processing of an inappropriate degree (the degree of revision, etc.) to the natural image.